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United States Patent |
5,598,894
|
Burleson
,   et al.
|
February 4, 1997
|
Select fire multiple drill string tester
Abstract
A system is provided for selectively perforating multiple zones in a well
either simultaneously, or in series, having isolation barriers, or
packers, located between the perforating multiple zones, without moving
the system with respect to the well. The system includes a tubing string
which carries at least a first and a second perforating gun. At least a
first and a second pressure actuated firing head are associated with the
first and second perforating guns, respectively. A first and second packer
for isolating the perforating guns from each other. A source of actuating
fluid pressure for the firing head is provided, which may be the bore of
the tubing string. A first selective communication device is provided for
isolating the second firing head from the source of actuating fluid
pressure until after the first perforating gun has been fired, and for
then communicating the second firing head with the source of actuating
fluid pressure in response to firing of the first perforating gun.
Inventors:
|
Burleson; John D. (Denton, TX);
George; Flint R. (Flower Mound, TX);
Mason; Justin L. (Denton, TX)
|
Assignee:
|
Halliburton Company (Dallas, TX)
|
Appl. No.:
|
498312 |
Filed:
|
July 5, 1995 |
Current U.S. Class: |
175/4.52; 166/55.1; 166/297; 175/4.54 |
Intern'l Class: |
E21B 029/02; E21B 043/117; E21B 043/118.5 |
Field of Search: |
175/4.52,4.54
166/55,55.1,297,63,264,142,191
|
References Cited
U.S. Patent Documents
3612189 | Oct., 1971 | Brooks et al. | 166/55.
|
4560000 | Dec., 1985 | Upchurch | 166/55.
|
4612992 | Sep., 1986 | Vann et al. | 175/4.
|
4619333 | Oct., 1986 | George | 175/4.
|
5103912 | Apr., 1992 | Flint | 175/4.
|
5287924 | Feb., 1994 | Burleson et al. | 166/297.
|
5355957 | Oct., 1994 | Burleson et al. | 166/297.
|
Primary Examiner: Novosad; Stephen J.
Attorney, Agent or Firm: Imwalle; William M., Herman; Paul I., Perez; Daniel F.
Claims
What is claimed is:
1. A system for selectively perforating multiple zones in a well,
comprising:
a tubing string;
at least a first and a second perforating gun carried on said tubing
string, each said perforating gun having a pressure actuated firing head
associated therewith;
a source of actuating fluid pressure for said firing heads;
at least a first and a second packer connected to said tubing string and
associated with said first and second perforating guns such that said
perforating guns are isolated with respect to the other; and
at least a first and a second communication means for selectively actuating
said pressure actuated firing heads to cause said perforating guns to
perforate zones in a well.
2. A system of claim 1, wherein said second packer being positioned above
said second perforating gun and said first packer being positioned between
said first and said second perforating guns.
3. A system of claim 1, wherein said first and second communication means
isolates said second firing head from said source of actuating fluid
pressure until after said first firing head has been actuated and for then
communicating said firing head with said source of actuating fluid
pressure in response to actuation of said first firing head.
4. The system of claim 1, further comprising:
a total number X of said pressure actuated firing heads including said
first and second firing heads; and
a total number X-1 of said selective communication means including said
first selective communication means.
5. The system of claim 3, wherein:
said first selective communication means includes a select fire sub
including:
a housing having a first chamber defined therein communicated with said
second firing head;
a supply passage communicated with said source of actuating fluid pressure
and extending into said housing, said supply passage initially being
isolated from said first chamber; and
explosive means for perforating a portion of said housing and thereby
communicating said supply passage with said first chamber.
6. The system of claim 5, wherein:
said housing of said select fire sub has a second chamber defined therein
in addition to said first chamber, said chambers being initially separated
by a wall; and
said explosive means is disposed in said second chamber and is a means for
perforating said wall.
7. The system of claim 6, wherein:
said supply passage extends into said wall, said wall being said portion of
said housing perforated by said explosive means to communicate said supply
passage with said first chamber.
8. The system of claim 5, further comprising:
actuating means for firing said explosive means of said select fire sub in
response to firing of said first perforating gun.
9. The system of claim 5, wherein:
said source of actuating fluid pressure includes a well annulus surrounding
said select fire sub, said supply passage being open to said well annulus;
and
said select fire sub is constructed so that when said explosive means
perforates said portion of said housing, said first chamber is
communicated with said well annulus.
10. An apparatus for isolating a plurality of perforating guns in a well,
comprising:
a tubing string having the plurality of perforating guns connected thereto
a predetermined location;
a plurality of packers connected to said tubing string and positioned above
said corresponding perforating gun, said plurality of packers isolate said
adjacent perforating guns from each other when positioned;
a pressure actuated firing head associated with each said perforating gun;
and
a source of actuating fluid for said firing heads which operates when
pressurized to cause the firing heads to selectively fire the perforating
guns.
11. An apparatus of claim 11, wherein the selective firing of the
perforating guns is performed simultaneously.
12. An apparatus of claim 12, wherein the selective firing of the
perforating guns is performed in series.
13. A method of perforating multiple zones in a well comprising the steps
of:
(a) running into said well a tubing conveyed multiple zones perforating
string including:
a tubing string;
at least a first and a second perforating guns carried by said tubing
string;
at least a first and second pressure actuated firing head associated with
said first and second perforating guns, respectively; and
at least a first and a second packer connected to said tubing string and
associated with said first and second perforating guns, said first packer
being positioned above said first perforating gun and said second packer
being positioned between said first and said second perforating guns;
(b) isolating said first and said second perforating guns by setting said
first and said second packer in the well;
(c) firing said first and said second perforating guns by applying
actuating fluid pressure from a source of actuating fluid pressure to said
firing heads contained on said perforating guns.
14. A method of claim 13, wherein said firing of said first and said second
perforating guns is performed simultaneously.
15. A method of claim 13, wherein said firing step of said second
perforating gun is performed subsequent to said firing step of said first
perforating gun.
16. A method of claim 14, wherein said firing step comprises the steps of:
(a) applying actuating fluid pressure from a source of actuating fluid
pressure to said first firing head;
(b) isolating said second firing head from said source of said actuating
fluid pressure during step (a);
(c) after step (a), firing said first perforating gun; and
(d) in response to firing said first perforating gun in step (c),
communicating said firing head with said source of said actuating fluid
pressure.
17. The method of claim 16, further comprising:
between steps (a) and (c), bleeding off said actuating fluid pressure.
18. The method of claim 17, further comprising:
during step (d), isolating said second firing head from said first
perforating gun.
19. The method of claim 17, further comprising:
applying actuating fluid pressure to said second firing head; and
firing said second perforating gun.
20. The method of claim 19, further comprising:
firing said perforating guns sequentially from the bottom up, said first
perforating gun being located below said second perforating gun.
21. The method of claim 19, further comprising:
firing said perforating guns sequentially from the top down, said first
perforating gun being located above said second perforating gun.
22. The method of claim 17, wherein:
step (b) includes isolating said second firing head from said source of
actuating fluid pressure with a wall; and
step (d) includes detonating an explosive charge to perforate said wall and
thereby communicate said second firing head with said source of actuating
fluid pressure.
23. The method of claim 17, further comprising:
flow testing a subsurface zone perforated by said first perforating gun.
24. The method of claim 23, further comprising:
prior to step (c), isolating said subsurface zone between upper and lower
packer elements carried by said tubing string.
25. The method of claim 16, further comprising the step of isolating the
lower perforating guns to selectively test the drill string.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of well perforating.
2. Description of the Prior Art
During the completion of an oil or gas well, a length of casing is cemented
in a borehole, and then one or more zones of the casing are perforated to
communicate the bore of the casing with subsurface geological formations
intersected by the borehole so that oil or gas from that subsurface
formation may be produced by the well.
One well-known type of perforating system is a tubing conveyed perforating
system wherein the perforating guns and related apparatus are carried by a
tubing string made up of a plurality of threaded joints of tubing or pipe
which are connected together and lowered into the well. These tubing
conveyed completion systems may be run in combination with a drill stem
test string so that the well can be perforated and tested in a single
trip.
In some situations, it is desirable to be able to selectively perforate
more than one zone of the well at different times. The prior art has
typically addressed this need by the provision of multiple firing heads
which are constructed to actuate at different operating pressures. With
these systems, the selection of the appropriate firing head and gun to be
fired is determined by the pressure which is applied to the tubing string
or the well annulus to actuate the firing head. Systems of this type
capable of firing several perforating guns independently during one trip
into the well can be constructed utilizing the Time Delayed Firing Head
available from Halliburton Energy Services. The Halliburton Time Delayed
Firing Head utilizes a set of shear pins the number of which can be
selected to determine the actuating pressure of each firing head.
Two recent patents assigned to the assignee of the present invention relate
to systems for selective perforation of a well in multiple zones. Those
patents are U.S. Pat. No. 5,287,924 issued on Feb. 22, 1994, entitled,
"Tubing Conveyed Selective Fired Perforating Systems," and U.S. Pat. No.
5,355,957 issued on Oct. 18, 1994, entitled, "Combined Pressure Testing
and Selective Fire Perforating Systems," both having common inventors to
the subject invention.
SUMMARY OF THE INVENTION
The present invention provides a tubing conveyed selective fired
perforating system for selectively perforating multiple zones of a well
having isolation barriers, or packers, located between the multiple
perforating guns to permit selective perforation of the zones either
simultaneously, or in series, without moving the system with respect to
the well. In addition, the present invention discloses the use of a
selective perforation system in conjunction with a selective drill string
testing system.
The system includes a tubing string carrying at least a first and a second
perforating gun. At least a first and a second pressure actuated firing
head are associated with the first and second perforating guns,
respectively.
A source of actuating fluid pressure for the firing heads is provided. The
source is preferably either the tubing bore of the tubing string or the
well annulus surrounding the tubing string.
A first packer is provided for isolating the first and second perforating
gun by being connected to the tubing string between the first and second
perforating guns and selectively set within the bore of the well. In
addition, a second packer is connected above the second perforating gun,
and likewise, selectively set within the bore of the well.
When operating the perforating guns in a series, a first selective
communication means is provided for isolating the second firing head from
the source of actuating fluid pressure until after the first perforating
gun has been fired, and for then communicating the second firing head with
the source of actuating fluid pressure in response to firing of the first
perforating gun.
Additional selective communication means can be provided to allow for
firing of additional perforating guns selectively in sequence.
The selective communication means preferably is a select fire sub including
a housing having a first chamber defined therein. The first chamber is
communicated with the second firing head. A supply passage is communicated
with the source of actuating fluid pressure and extends into the housing.
The supply passage is initially isolated from the first chamber. An
explosive means is contained in a second chamber of the housing for
perforating a portion of the housing and thereby communicating the supply
passage with the first chamber. An actuating means fires the explosive
means of the select fire sub in response to firing of the first
perforating gun.
In an alternative embodiment, the perforating guns can be operated
simultaneously, rather than in series as described above.
Numerous objects, features and advantages of the present invention will be
readily apparent to those skilled in the art upon a reading of the
following disclosure when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, including its
features and advantages, reference is now made to the detailed
description, taken in conjunction with the accompanying drawings of which:
FIG. 1 is an elevation schematic view of a first embodiment of the select
fire multiple drill string tester system of the present invention shown in
place in a well which intersects a plurality of subsurface geological
formations which are to be perforated;
FIG. 2 is an elevation sectioned view showing the details of construction
of an isolation sub assembly utilized in the system FIG. 1;
FIG. 3 is an elevation sectioned view showing the details of construction
of a select fire sub utilized with the system of FIG. 1;
FIG. 4 is an enlarged sectioned view of the gun delay/isolation device used
in the isolation sub of FIG. 2;
FIGS. 5A-5K are elevation sectioned views showing the details of
construction of the select fire multiple drill string tester system of
FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings, and particularly to FIG. 1, a well is shown
and generally designated by the numeral 10. The well 10 is formed by
drilling a borehole 12 into the ground and then placing a casing 14 within
the borehole 12 and cementing the casing in place with cement 16. The
casing 14 has a casing bore 18. The borehole 12 intersects one or more
subsurface geological formations such as 20 and 22 which are to be
perforated for testing and/or production of the well from those zones.
A perforating string 24 is shown in place in the well 10. The perforating
string 24 of the present invention may also be referred to as a tubing
conveyed selective fired perforating system 24. A well annulus 27 is
defined between the casing bore 18 and the perforating string 24.
The system 24 provides a means by which a plurality of perforating guns can
be selectively fired so as to selectively perforate multiple zones of the
well 10 such as the zones 20 and 22 illustrated in FIG. 1.
The system 24 includes a tubing string 26 which carries on its lower end a
string of tools which beginning from top to bottom include a first annular
pressure crossover assembly 28, a packer 30, tubing 32, a pressure
operated vent assembly 33, an annulus pressure crossover assembly 34, a
control line sub 35, a first air chamber 36, a first pressure activated
firing head 37, a first crossover 38, which connects firing head 37 to a
first select fire sub 40, a second air chamber 42, a second pressure
activated firing head 44, a second crossover sub 46, a second select fire
sub 48, a third air chamber 50, a third pressure activated firing head 52,
a third crossover sub 54, a first perforating gun 56, a fourth crossover
sub 58, a circulating valve 60, a slip joint 62, a safety joint 64, a
second packer 66, a perforated sub 68, tubing 70, a fourth pressure
activated firing head 72, a fifth crossover sub 74, a second perforating
gun 76, a sixth crossover sub 77, a fifth pressure activated firing head
79, and a ported sub 81.
It will be understood that each of the perforating guns schematically
illustrated in FIG. 1 may be made up of many individual gun segments
connected together in series to provide the proper length of gun to
perforate the zone in question.
The annulus pressure crossover assembly 34 is communicated with the first
select fire sub 40 by the first control fluid conduit portion 83. The
conduit 83 may be 1/4 inch O.D. stainless steel tubing. The first select
fire sub 40 is communicated to the second select fire sub 48 by a second
control fluid conduit portion 85. The second select fire sub 48 is
communicated to the circulating valve 60 by a third control fluid conduit
portion 87.
The system 24 is constructed for use with packers 30 and 66 and is arranged
to fire the perforating guns 56 and 76 selectively in sequence from the
bottom up. That is, the first gun to fire will be second gun 76. The next
gun to fire will be first gun 56. The system 24 may also fire the
perforating guns 56 and 76 simultaneously.
To selectively perforate multiple zones such as zones 20 and 22 of the well
10 with the system 24, the procedure is carried out as follows. System 24
is lowered into the casing bore 18 of well 10 placing first perforating
gun 56 adjacent to first subsurface zone 20 and placing second perforating
gun 76 adjacent to second subsurface zone 22.
The firing heads 37, 44, 52, 72 and 79 preferably are Time Delay Firing
Heads available from Halliburton Energy Services. These firing heads
employ a time delay fuse. The use of the time delay fuse allows for ample
time, on the order of five to seven minutes, to bleed the actuating
pressure off the tubing string 26 prior to the time the associated
perforating gun fires. The operating pressure of the firing head 79 is
determined by selection of the number of shear pins utilized to hold a
firing piston in place initially against the differential pressures acting
there across.
As seen in FIG. 2, an alternative embodiment of the present invention can
be seen which reflects the use of an isolation sub. Specifically, an upper
end 78 of second perforating gun 76 is threadedly connected at 80 to a
crossover sub 77. A detonating cord 84 extends from the upper end of
perforating gun 79 through the crossover sub 77 where it terminates in a
booster charge 86. The crossover sub 77 and components contained therein
may be considered to be a portion of the fifth perforating gun 79.
The crossover sub 77 is connected at thread 88 to a delay housing 90 of
isolation sub 89 with O-ring seals 92 being provided therebetween.
The delay housing 90 carries a booster charge 94 at its lower end which is
fired by the booster charge 86. The booster charge 94 in turn ignites a
length of detonating cord 96 which leads to a third booster charge 98
which fires a gun delay/isolation device 100.
The upper end portion of delay housing 90 has internal threads 102 which
are joined to external threads 104 of the fourth pressure activated firing
head 72. As will become apparent when viewing FIG. 3, the orientation of
the crossover sub may be inverted.
Now referring to FIG. 3, a drawing represent in first select fire sub 40 is
depicted. The booster charge 108 is contained in a cylindrical insert 110
which carries the booster 108, a length of detonating cord 112, and a
shaped charge 114.
The upper end first select fire sub 40 has external threads 104 which are
joined to internal threads 102 of a delay housing 90 similar to that
pictured in FIG. 2, so that a lower end 106 of gun delay/isolation device
100 abuts a booster charge 108 received in the first select fire sub 40.
The booster 108 is contained in a cylindrical insert 110 which carries the
booster 108, a length of detonation cord 112, and a shaped charge 114.
The gun delay/isolation device 100 when fired by the booster 98 will in
turn fire the booster 108, but at the same time will prevent fluid
communication through a bore 116 of delay housing 90 thereby maintaining
the first perforating gun 34 isolated from the select fire sub 38. The gun
delay/isolation device 100 works in the following manner.
As seen in FIG. 4, which is an enlarged sectioned view of the gun
delay/isolation device 100, device 100 includes a housing 170 received in
bore 116 with O-ring seals 171 and 172 received therebetween. Housing 170
has a bore 173, lower counterbore 174, upper counterbore 175, and upper
threaded counterbore 176 defining a central passage therethrough.
Upper counterbore 175 has an annular spacer 177 received therein abutting
shoulder 178. Located above spacer 177 is a primer cap 179.
Located above primer cap 179 is a piston sleeve 180 carrying O-rings 181
and 182 which seal against counterbore 175. Piston sleeve 180 is threaded
at 183 adjacent its upper end 184. Thread 183 is received in threaded
counterbore 176 to hold piston sleeve 180 in place.
A piston 185 is received in a bore 186 of piston sleeve 180 with two
O-rings 187 and 188 therebetween. Piston 185 has a radially outward
extending flange 189 at its upper end which is larger in diameter than
bore 186 and initially holds piston 185 in the position shown.
An annular retainer ring 190 is threadedly received in threaded counterbore
176 above piston 185 to prevent upward movement of piston 185.
Retainer ring 190 has booster 98 (see FIG. 2) received in a bore 191
thereof.
Below primer cap 179 the bore of spacer 177 and the bore 173 and
counterbore 174 of housing 170 are packed with an explosive mixture 192
which is held in place by a thin retainer disc 193 received in the lower
end of lower counterbore 174.
When booster 98 detonates, the high pressure generated thereby pushes down
on piston 185 shearing the radial flange 189. Piston 185 travels downward
within bore 186 a short distance until firing pin 194 of piston 185
strikes primer cap 179 detonating the same. The detonation of primer cap
179 detonates the explosive material 192 which will rupture disc 193 and
in turn detonate booster 108 (see FIG. 3). The burning of explosive
mixture 192 will also provide a short time delay in this explosive chain
reaction.
The piston 185 remains sealed in bore 186 of piston sleeve 180, thereby
preventing any fluid pressure communication through the device 100.
The device 100 is itself a part of the prior art and is constructed in
accordance with the teachings of U.S. Pat. No. 5,078,210 to George, the
details of which are incorporated herein by reference.
The select fire sub 40 is shown in detail in FIG. 3. Select fire sub 40
includes a cylindrical housing 118 which can be described as having first
and second ends 120 and 122 which may also be referred to as lower and
upper ends 120 and 122 in the orientation shown in FIG. 3.
The housing 118 of select fire sub 40 has first and second axially
extending chambers 124 and 126 defined therein and communicated with the
first and second ends 120 and 122, respectively, of housing 118. The first
chamber 124 is defined by a bore 128 which has a blind end 130. The second
chamber 126 is defined by a bore 132 and a counterbore 134. The bore 132
has a blind end 136.
The blind ends 130 and 136 of chambers 124 and 126 are separated by a wall
138 of housing 118.
The housing 118 has an actuating pressure supply passage 140 defined
therein. Supply passage 140 includes a lateral bore 142 extending
laterally into the wall 138 between the blind ends 130 and 136 of first
and second chambers 124 and 126.
Housing 118 includes a cylindrical outer surface 144 having first and
second recesses 146 and 148 defined therein on opposite sides
longitudinally of the lateral bore 142.
The actuating pressure supply passage 140 further includes first and second
branch passages 150 and 152 communicating the lateral bore 142 with the
first and second recesses 146 and 148, respectively. Each of the branch
passages 150 and 152 includes an internally threaded outermost portion
such as 154 and 156 which provides a means for connection thereof to a
control fluid conduit such as first control fluid conduit portion 83 which
extends into the first recess 148 and second control fluid conduit portion
85 which extends into the first recess 146.
It is noted that for the configuration as shown in figure FIG. 1 which is
shown in detail in FIG. 3, the threaded outer portion 160 of lateral bore
142 is blocked by a threaded plug 162.
The lower portion of select fire sub 40 carries external threads 164 which
are connected to the second air chamber 42 seen in FIG. 1.
Referring now to FIGS. 5A-K, drawing depicting the details of construction
of the select fire multiple drill string tester system of the present
invention are shown. FIG. 5A depict an upper section of system 24
including a first annular pressure crossover assembly 28 and a packer 30.
FIG. 5B shows tubing 32, a pressure operated vent assembly 33, an annulus
pressure crossover assembly 34, a control line sub 35 and first control
fluid conduit 83 of the system 24.
FIG. 5C depicts a first air chamber 36, a first pressure activated firing
head 37, a first crossover 38, a first select fire sub 40, and first and
second control fluid conduits 83 and 85 of system 24. A second air chamber
42, a second pressure activated firing head 44, a second crossover sub 46,
a second select fire sub 48, and second and third control fluid conduits
85 and 87 are pictured in FIG. 5D. In FIG. 5E a third air chamber 50, a
third pressure activated firing head 52, a third crossover sub 54, and
third control fluid conduit 87 are depicted.
FIG. 5F shows a first perforating gun 56, a fourth solid crossover sub 87,
a circulating valve 60, and third control fluid conduit of system 24. A
slip joint 62 is depicted in FIG. 5G, a safety joint 64 is depicted in
FIG. 5H and a second packer 66 is depicted in FIG. 5I. FIG. 5J shows a
perforated sub 68, tubing 70, and a fourth pressure activated firing head
72. FIG. 5K shows a fifth crossover sub 74, a second perforating gun 76, a
sixth crossover sub 77, a fifth pressure activated firing head 79, and a
ported sub 81 of system 24.
OPERATION
The present invention can be further understood by reference to the
previously disclosed detailed description and drawings in conjunction with
the operation of the system. Set forth below is a preferred embodiment of
the invention disclosing the operating procedures for the system.
In operation, the test string is run in the hole. After the test string is
set for RTTS (retrievable treat test squeeze). By way of example, the
system can be performed on a 1925 feet test well at Halliburton Energy
Services North Test Well located in Carrollton, Tex. Next, the surface
pressure is increased to 1200 psi to set the right hand (RH) packer, and
the pressure is held for 5 minutes. To verify that the packer has been
set, a pressure of 5000 psi is pulled.
The tubing pressure is continued up from 1175 psi to 2294 psi surface
pressure to open the pressure operated vent (POV) and the pressure is
subsequently released immediately while ensuring that the annulus valves
are open. By way of example, the valve can be the 7-9-5/8" annulus valves.
The 3-1/2-7 annulus is pressured to 1700 psi surface pressure and held to
activate select tester to be ready for close-in. The tubing pressure is
allowed to reduce to 829 psi surface pressure to fire the button time
delay fire perforating guns. Then, the annulus is pumped down to simulate
flow at 1/2 BPM.
Next, the pressure is bled on the 3-1/2-7" annulus to close select tester
for closed-in time, while letting 7-9-5/8" annulus build up to 1000 psi to
show closure. The 3-1/2-7" annulus is pressured to 1000 psi to cycle the
Omni valve around the first well position. On the last pressure up cycle
going into the well test, the surface pressure is continued to 1700 psi
which opens the select tester and allowing the 7-9-5/8" annulus to flow at
1/2 BPM. In addition, surface pressure is continued up to 2577 psi to
close a Vann Circulating Vent (VCV). This will isolate the bottom interval
and fire either the No. 1 or 2 upper TDF's and lock the select tester
open.
During the Drill String Testing (DST) of the lower perforated interval, the
flow is coming into the drillstring through the open ports of the VCV.
When the DST of the lower interval has been completed the VCV is caused to
shut by applying the appropriate annulus pressure. This causes a sleeve in
the VCV to seal across the open ports, and prevents any further flow from
the lower interval into the drillstring. This is the first step in
preparing for further DST of upper zones.
The 7-9-5/8" annulus is allowed to build pressure to 1000 psi to show the
VCV closure. The system has an option to either bleed annulus off to 250
psi to monitor TDF firing or to maintain annulus pressure until all TDF's
fire. If the first option is selected, pressure is applied to the annulus
to 2500 psi to lock the select tester and fire remaining TDF's, making
sure to hold pressure for 15 minutes. If closure is desired, release
3-1/2-7" annulus pressure and build back up to 2500 psi to unlock select
tester and release back at 0 psi surface pressure for select tester
closure. If, however, closure is not desired, simply release pressure on
the 3-1/2-7" annulus.
Finally, pull a 28,000 psi pressure to release the RH packer. The tubing
string is pulled to release the RTTS. The last step is pulling out of the
hole.
The gun system for each zone to be perforated may be custom designed since
the guns used to perforate the other zones will be isolated therefrom by a
packer. This means there will not be constraints with respect to the
length of the gun (or series of guns) or their distance from the isolating
packer(s). This is not only a benefit over the other known systems, but
also is a primary differentiating factor over the known prior art.
If all the gun systems are designed on the string to be properly located at
one time (that is without having to move the string to orient the guns at
the various zones), then each gun system may be actuated simultaneously,
or in series. Because there are packers between each zone, different zones
will not influence the others.
Thus it is seen that the apparatus and methods of the present invention
readily achieve the ends and advantages mentioned as well as those
inherent therein. While certain preferred embodiments of the invention
have been illustrated and described for purposes of the present
disclosure, numerous changes may be made by those skilled in the art,
which changes are encompassed within the scope and spirit of the present
invention as defined by the appended claims.
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